System and Method for Carrying Control Data in a Preamble

ABSTRACT

A system and method for carrying control data in a preamble. A control-data bearing preamble is defined to facilitate end-to-end labeling and control-data transport. This control-data bearing preamble provides a unified labeling scheme with minimal overhead, which facilitates greater ease in parsing. The control-data bearing preamble can be converted to/from other control/labeling schemes at the edge of the control-data bearing preamble aware portion of the network.

This application claims priority to provisional application No.61/755,751, filed Jan. 23, 2013, which is incorporated herein byreference in its entirety.

BACKGROUND Field of the Invention

The present invention relates generally to networking and, moreparticularly, to a system and method for carrying control data in apreamble.

INTRODUCTION

Data communication networks continue to expand in reach and capacity.The continual evolution of data communication networks presentscontinuing challenges in coordinating the transport of various forms ofnetwork traffic from various sources. Interconnection of customernetworks (e.g., residential), access networks, and metro/core networkspresents significant challenges in addressing the various quality ofservice (QoS) domains represented.

BRIEF DESCRIPTION OF THE DRAWINGS

In order to describe the manner in which the above-recited and otheradvantages and features of the invention can be obtained, a moreparticular description of the invention briefly described above will berendered by reference to specific embodiments thereof which areillustrated in the appended drawings. Understanding that these drawingsdepict only typical embodiments of the invention and are not thereforeto be considered limiting of its scope, the invention will be describedand explained with additional specificity and detail through the use ofthe accompanying drawings in which:

FIG. 1 illustrates an example of communication across multiple QoSdomains.

FIG. 2 illustrates example embodiments of a preamble of an Ethernetframe containing control data.

FIG. 3 illustrates an example of a control data bearing preamble awareportion of a network.

FIG. 4 illustrates an example process of the present invention.

DETAILED DESCRIPTION

Various embodiments of the invention are discussed in detail below.While specific implementations are discussed, it should be understoodthat this is done for illustration purposes only. A person skilled inthe relevant art will recognize that other components and configurationsmay be used without parting from the spirit and scope of the invention.

Customer networks, access networks, and metro/core networks provide atransport framework for today's data communications needs. Variousnetwork labeling schemes such as multiprotocol label switching (MPLS),virtual local area networks (VLANs), stacked VLANs, MAC-in-MAC, etc.that are used in such networks can add significant overhead. As aconsequence, the multiple label-mapping stages can add significantoverhead and cost.

In accordance with the present invention, a control-data bearingpreamble is defined to facilitate end-to-end labeling and control-datatransport. This control-data bearing preamble can provide a unifiedlabeling scheme with minimal overhead, which facilitates greater ease incontrol data parsing. The control-data bearing preamble can be convertedto/from other control/labeling schemes at the edge of the control-databearing preamble aware portion of the network. As an example, the use ofthe control-data bearing preamble in the metro/core portion of thenetwork allows one-for-one mapping of labeling schemes used in an accessportion of the network (e.g., EPON).

In one embodiment, a first Ethernet frame having a preamble thatincludes control data associated with network traffic contained withinthe first Ethernet frame is received in a first network node in anaccess network. The first network node can then transmit a secondEthernet frame based on the first Ethernet frame to a second networknode in a metro/core network, wherein the second Ethernet frame has apreamble that includes at least part of the control data included in thepreamble of the first Ethernet frame. End-to-end labeling for thenetwork traffic across the access and metro/core networks is therebyfacilitated. In various examples, the control data in the preamble ofthe Ethernet frame can identify a data flow, a packet sequence number,time critical control information (e.g., protection switching,synchronization, etc.), etc. More generally, the control data in thepreamble of the Ethernet frame can provide an out-of-band managementchannel.

In another embodiment, intermediate nodes in the control-data bearingpreamble aware portion of the network can modify the control data in thepreamble of the Ethernet frame. In one example, a first Ethernet framehaving a first preamble that includes first control data associated withnetwork traffic contained within the first Ethernet frame is received bya first network node. The first network node can then modify thecontents of the first preamble to produce a second preamble, wherein themodified contents includes second control data associated with thenetwork traffic contained within the first Ethernet frame, the secondcontrol data being different from the first control data. Next, thefirst network node transmits a second Ethernet frame based on the firstEthernet frame to a second network node, wherein the second Ethernetframe includes the second preamble having the second control dataassociated with the network traffic.

To further illustrate the features of the present invention, referenceis made first to FIG. 1 which illustrates an example of communicationacross multiple QoS domains. As illustrated, an end-to-end service isprovided that couples server 110 in customer network 101 to client 120in customer network 105. This end-to-end service traverses varioustransport networks such as access network 102, metro/core network 103,and access network 104. As would be appreciated, the particular form ofthe individual networks 101-105 can vary. In various examples, customernetworks 101, 105 can represent residential or business networks, accessnetworks 102, 104 can represent passive optical network (PON), Data OverCable Service Interface Specification (DOCSIS), Wi-Fi, etc. networks,and metro/core network 103 can represent a carrier network. Regardlessof the particular implementation within a particular network 101-105,each such network can represent a different label and QoS domain.

To facilitate transport between each adjacent pair of the variousnetworks 101-105, a mapping function is provided at the interfacebetween adjacent networks. As illustrated, mapper 131 provides a mappingfunction between customer network 101 and access network 102, mapper 132provides a mapping function between access network 102 and metro/corenetwork 103, mapper 133 provides a mapping function between metro/corenetwork 103 and access network 104, and mapper 134 provides a mappingfunction between access network 104 and customer network 105.

The illustration of mappers 131-134 in FIG. 1 is representative of afunctional block that can be performed by one or more network nodes atthe interface between two networks. Consider, for example, a PON-basedaccess network. In this example, the functionality of mapper 131 betweencustomer network 101 and access network 102 can be implemented by anoptical network unit (ONU), which includes a switching subsystem as partof its service-specific function. This switching subsystem facilitates aconnection of the ONU to a client-facing network via a plurality ofnetwork interfaces that are designed to support a plurality ofsubscriber connections. The functionality of mapper 132, on the otherhand, can be implemented by an optical line terminal (OLT). In apoint-to-multipoint system such as PON, a single OLT at a head end canbe designed to communicate with a plurality of ONUs at various endnodes.

In this example of a PON-based access network, the labeling and QoSdomain is facilitated by a logical link identifier (LLID) that isassigned by an OLT to an ONU. This LLID is communicated end-to-endacross the PON domain for management of PON services delivered to theONU. At the OLT, the LLID is removed from the Ethernet traffic prior todelivery of the traffic to the metro/core network.

As this example illustrates, each of the individual networks 101-105 canuse different labels to facilitate the individual QoS domains. As such,a stacking of labels can result as traffic traverses the variousnetworks. Such stacking of labels leads to increased overhead and cost.

It is a feature of the present invention that an end-to-end labelingscheme is provided using the 8-byte preamble of an Ethernet frame. Morespecifically, the 8-byte preamble of the Ethernet frame is used to carrycontrol data across various networks in an end-to-end service. A furtherbenefit of transporting control data in the preamble is the reducedprocessing afforded by the simple parsing of control data at thefront-end of the Ethernet frame. As would be appreciated, a conventionalEthernet frame includes a preamble followed by one or more headers and apayload portion.

FIG. 2 illustrates example embodiments of a preamble of an Ethernetframe containing control data. As illustrated, the 8-byte preamble caninclude a single-byte start control data delimeter (SCD), a control dataportion spanning a plurality of bytes, and an optional error detectingcode portion such as a CRC8 or CRC16 field. As would be appreciated, theparticular format of the preamble of the Ethernet frame can vary.Regardless of the format, the inclusion of one or more bytes of controldata enables end-to-end labeling or other control-data transport infacilitating a control-data preamble aware portion of the network.

FIG. 3 illustrates an example of a control-data bearing preamble awareportion of a network. As illustrated, an end-to-end service is providedthat couples server 310 in customer network 301 to client 320 incustomer network 305. This end-to-end service traverses varioustransport networks such as access network 302, metro/core network 303,and access network 304.

To facilitate transport between customer network 301 and access network302, a mapping function is provided at the interface by mapper 331. Atmapper 331, control data can be added to the preamble of the Ethernetframe and passed on to the various intermediate nodes in access network302, metro/core network 303 and access network 304. Mapper 332 at theinterface between access network 304 and customer network 305 can removethe control data from the preamble of the Ethernet frame and pass theEthernet frame to customer network 305. By adding/removing control datato/from the preamble at mappers 331/332, a single label and QoS domainis created across access network 302, metro/core network 303 and accessnetwork 304. This single label and QoS domain effects reduced processingthrough the low overhead implementation of control data in the preambleof the Ethernet frame. In general, the control-data bearing preamble canbe converted to and from other control/labeling schemes such as VLANtagging, 802.1Q, 802.1ah, MPLS, etc. at the edge of the control-databearing preamble aware portion of the network.

Unlike the communication of traffic across the multiple label and QoSdomains illustrated in FIG. 1, the interfaces between the accessnetworks 302, 304 and metro/core network 303 need not remove, replace,or modify labeling or other control data prior to passage to the nextnetwork. A unified labeling scheme across access network 302, metro/corenetwork 303 and access network 304 thereby results. For example, wherethe control-data bearing preamble is received at an OLT in accessnetwork 302, the OLT can simply pass on traffic that retains the controldata in the preamble of the Ethernet frame to metro/core network 303. Assuch, the OLT operates as an intermediary node in the end-to-end serviceand need not remove, replace, or modify labeling or other control datainserted into the preamble at the interface between customer network 301and access network 302.

It is a feature of the present invention that the creation of acontrol-data preamble aware portion of the network enables variouscontrol-data based applications to be applied across a network boundary.As would be appreciated, the particular control-data based applicationthat can be facilitated by a control-data bearing preamble would beimplementation dependent.

In one example, the control data can be used to identify data flows in amanner similar to MPLS labels. In another example, the control data canbe used to carry packet sequence numbers. In another example, thecontrol data can facilitate an out-of-band management channel that canprovide support for alarm and failure notifications, encryption keyexchange, or any other operations, administration, maintenance, and/orprovisioning application. In another example, the control data canfacilitate the transport of time-critical control information such asprotection switching information, synchronization, or the like.

In yet another example, the control-data bearing preamble can be used toallow for one-to-one mapping of access-network labeling schemes (e.g.,PON, DOCSIS, Wi-Fi, etc.) to the metro/core network. For instance, theEPON LLID in the access network can be used in the metro/core network.In another instance, a “super-EPON” format can be defined that is basedon an identifier that uniquely specifies the PON port together with theLLID, or a “super-GPON” format can be defined that is based on anidentifier that uniquely specifies the PON port together with aGPON-specific ID such as the Alloc_ID or GEM Port ID, or a“super_DOCSIS” format can be defined that is based on an identifier thatuniquely specifies the CMTS port together with the SSID.

In general, it is recognized that the large address space afforded bythe 8-byte preamble of the Ethernet frame can be used to eliminate theneed for stacked labeling (e.g., stacked VLANs, stacked MPLS, etc.) invarious applications.

In addition to the forwarding of control data across a network boundary,an intermediate node can also modify the control data contained in thepreamble. For instance, consider an example where a labeling scheme isused to determine both the path and the treatment of the Ethernet framespassing through a given node. In one scenario, the intermediate node maymodify all or part of the control data to change the path or treatmentof the Ethernet frame.

This scenario can be evident in a protected network where both a primarypath and a backup path are operational. Here, a frame flow label caninstruct intermediate nodes to forward a given FTP packet along theprimary path and with high QoS, but when the primary path fails, thenode nearest to the failure can replace the label and forward the frameto the backup path. Since the backup path now serves all flows that wereoriginally using this path plus the new flows that were switched overfrom the primary path, QoS treatment for some flows may change. Table 1below illustrates an example treatment.

TABLE 1 Flow Before Protection Switching, After Protection Switching,(Service) Label Denotes Label Denotes A (VoIP) Primary Path + High QoSSecondary Path + High QoS B (FTP) Primary Path + High QoS SecondaryPath + Low QoS C (VoIP) Secondary Path + High QoS Secondary Path + HighQoS D (FTP) Secondary Path + High QoS Secondary Path + Low QoS

Having described a general framework of operation of a control-databearing preamble aware portion of a network, reference is now made toFIG. 4, which illustrates a flowchart of a process of the presentinvention. As illustrated, the process begins at step 402 where a firstEthernet frame having a first preamble that includes control data isreceived in a first network node. Where the first network node is on aninterface between two networks (e.g., access network and metro/corenetwork), the first network node can prepare at step 404 a secondEthernet frame based on the first Ethernet frame for transmission to thesecond network.

In one example, the control data in the preamble of the first Ethernetframe would be retained in the preamble of the second Ethernet frame.This illustrates a scenario where labeling (e.g., LLID) or other controldata application is extended across a network boundary. In anotherexample, the control data in the preamble of the first Ethernet frame ismodified at least in part relative to the control data in the preambleof the second Ethernet frame. This scenario illustrates the potentialusage of the control-data bearing preamble to facilitate applicationssuch as a protected network or other dynamic traffic handling.Regardless of the particular type and usage of the control data in thepreamble, it is significant that the passage of Ethernet traffic acrossa network boundary retains control data to facilitate a unified labeland QoS domain.

After the second Ethernet frame having a second preamble with controldata is created, the second Ethernet frame is then transmitted to asecond network node at step 406. The passage of control data using thepreamble portion of the Ethernet frame thereby facilitates an efficientcontrol data passing mechanism.

In general, the control-data bearing preamble offers an efficient andunambiguous mechanism to construct end-to-end labeling and QoS solutionsfor services that cross multiple transport boundaries. Significantly,the fixed size and location of the control-data bearing preamble enablesthe control data information to be easy to parse as compared to embeddedlabeling schemes that can be nested behind other information.

Another embodiment of the invention may provide a machine and/orcomputer readable storage and/or medium, having stored thereon, amachine code and/or a computer program having at least one code sectionexecutable by a machine and/or a computer, thereby causing the machineand/or computer to perform the steps as described herein.

These and other aspects of the present invention will become apparent tothose skilled in the art by a review of the preceding detaileddescription. Although a number of salient features of the presentinvention have been described above, the invention is capable of otherembodiments and of being practiced and carried out in various ways thatwould be apparent to one of ordinary skill in the art after reading thedisclosed invention, therefore the above description should not beconsidered to be exclusive of these other embodiments. Also, it is to beunderstood that the phraseology and terminology employed herein are forthe purposes of description and should not be regarded as limiting.

What is claimed is:
 1. An optical line terminal, comprising: an opticalreceiver that is configured to communicate with a plurality of opticalnetwork units via a point-to-multipoint network, said optical receiverbeing further configured to receive a first Ethernet frame having apreamble that includes control data associated with network trafficcontained within said first Ethernet frame; and a network interface thatis coupled to a network node in a metro or core network, said networkinterface being configured to transmit to said network node in saidmetro or core network a second Ethernet frame based on said firstEthernet frame, said second Ethernet frame having a preamble thatincludes at least part of said control data included in said preamble ofsaid first Ethernet frame.
 2. The method of claim 1, wherein said firstEthernet frame further includes one or more headers.
 3. The optical lineterminal of claim 1, wherein said control data provides end-to-endlabeling for said network traffic.
 4. The optical line terminal of claim1, wherein said control data identifies a data flow.
 5. The optical lineterminal of claim 1, wherein said control data identifies a packetsequence number.
 6. The optical line terminal of claim 1, wherein saidcontrol data provides an out-of-band management channel.
 7. A method,comprising: receiving, in a first network node in an access network, afirst Ethernet frame having a preamble that includes control dataassociated with network traffic contained within said first Ethernetframe; and transmitting, from said first network node in said accessnetwork to a second network node in a metro or core network, a secondEthernet frame based on said first Ethernet frame, said second Ethernetframe having a preamble that includes at least part of said control dataincluded in said preamble of said first Ethernet frame.
 8. The method ofclaim 7, wherein said first Ethernet frame further includes one or moreheaders.
 9. The method of claim 7, wherein said control data providesend-to-end labeling for said network traffic.
 10. The method of claim 7,wherein said control data identifies a data flow.
 11. The method ofclaim 7, wherein said control data identifies a packet sequence number.12. The method of claim 7, wherein said control data provides anout-of-band management channel.
 13. A method, comprising: receiving, bya first network node, a first Ethernet frame having a first preamblethat includes first control data associated with network trafficcontained within said first Ethernet frame; modifying, by said firstnetwork node, contents of said first preamble to produce a secondpreamble, said modified contents including second control dataassociated with said network traffic contained within said firstEthernet frame, said second control data being different from said firstcontrol data; and transmitting, by said first network node to a secondnetwork node, a second Ethernet frame based on said first Ethernetframe, said second Ethernet frame including said second preamble havingsaid second control data associated with said network traffic.
 14. Themethod of claim 13, wherein said first Ethernet frame further includesone or more headers.
 15. The method of claim 13, wherein said secondcontrol data replaces at least part of said first control data.
 16. Themethod of claim 13, wherein said second Ethernet frame also includessaid first control data.
 17. The method of claim 13, wherein saidcontrol data provides end-to-end labeling for said network traffic. 18.The method of claim 13, wherein said first control data identifies adata flow.
 19. The method of claim 13, wherein said first control dataidentifies a packet sequence number.
 20. The method of claim 13, whereinsaid first control data provides an out-of-band management channel.